syntax of cmake "get_filename_component" changed after version 2.8.11

for cmake version < 2.8.11
  get_filename_component(<VAR> <FileName> PATH [CACHE])

for cmake version >= 2.8.11
  get_filename_component(<VAR> <FileName> DIRECTORY [CACHE])

Update OpenCVConfig.cmake

Update OpenCVConfig.cmake.in